The deterioration mechanisms that take place in dental amalgam restorations while they are exposed to attack by the oral environment and simultaneously subjected to biting forces, will be studied in vivo using a unique "Dynamic Corrosion-Wear Cell." This experimental apparatus offers the ability to vary and measure electrochemical and mechanical parameters during a sliding-wear process in a corroding environment simulating mastication conditions. The compatibility and performance of several dental materials under corrosion and wear conditons operating simultaneously will be evaluated, and the role of critical material parameters such as composition, structure, and phases present will be determined. All testing will be conducted in simulated saliva and will include potentiostatic polarization scans, current-time and potential-time measurements under loading and no-loading conditions. Scanning electron microscopy will be performed to characterize specimens prior to and after testing. Solution chemistry will be analyzed by using atomic absorption spectroscopy to determine soluble products, resulting from the combined action of corrosion and wear, that may have direct biological effects. Main emphasis will be given to understanding the mechanisms of this deterioration process that may result in highly localized attack or marginal failure of restoration materials. Such understanding will provide the means to modify and improve existing dental materials or develop new ones.